Electroforming nickel copper alloys

ABSTRACT

A process for electroforming a nickel copper alloy by utilization of a nickel anode in an electrolyte solution containing copper, nickel and boric acid.

United States Patent [1 1 Olson et al.

[451 Sept. 3, 1974 ELECTROFORMING NICKEL COPPER ALLOYS Inventors: Roger A. Olson, Amery, Wis; Pat F. Mentone, St. Paul, Minn.

Assignee: Buckbel-Mears Company, St. Paul,

Minn.

Filed: Dec. 18, 1972 Appl. No.: 316,278

References Cited UNITED STATES PATENTS 1,750,092 5/1930 Crawford 204/44 1,951,893 3/1934 Winkler, Jr. 204/44 1,969,553 8/1934 Gernes 204/44 2,575,712 11/1951 Jernstedt 204/44 2,951,978 9/1960 Dickson et al 204/44 FOREIGN PATENTS OR APPLICATIONS 957,808 5/1964 Great Britain 204/44 Primary Examiner-T. M. Tufariello Attorney, Agent, or Firm-Jacobson and Johnson [5 7 ABSTRACT A process for electroforming a nickel copper alloy by utilization of a nickel anode in an electrolyte solution containing copper, nickel and boric acid.

9 Claims, 3 Drawing Figures 4 s POWER I SUPPLY w 18 PULSE til-ii GENERATOR ELECTROFORMING NICKEL COPPER ALLOYS BACKGROUND OF THE INVENTION 1 DESCRIPTION OF THE PRIOR ART Alloys such as copper nickel alloys are well known in the art and have numerous applications as resistors in electrical circuits. That is, the copper nickel alloy is a particularly useful alloy because the resistance of the alloy varies as the concentration of copper and nickel in the alloy varies. Thus, copper nickel alloys have numerous applications in the industry, particularly the electronics industry where they are used as resistors in electrical circuits. The present methods of manufacturing copper nickel alloys for use in electronic circuits is to alloy nickel and copper into sheet form and then cold roll the copper nickel alloy sheet to the desired thickness. Next, one cuts or etches out the section of the sheet to form the proper resistance. The difficulty with this particular process is that it is quite costly to cold roll an alloy until one obtains the proper thickness. In addition, this process requires that the alloy be fastened or mounted in the circuit. The present invention, in contrast, provides a method of electroforming a nickel copper alloy onto a mandrel where it can be later stripped from or electroplating the copper nickel alloy directly onto an electrical circuit.

While there are known processes of forming alloys by electroplating, it is believed that no practical or useable concepts of electroplating or electrofonning an alloy electroplating solution contains copper, nickel and boric acid.

In order to electroplate a nickel copper alloy, one

, must have the proper electroplating solution. Presently,

consisting of copper and nickel can find precedence in the prior art. That is, to date, no one has formed a true nickel copper alloy by electroplating or electroforming. Typically, what happens is that one component of the alloy will plate out and then the other component of the alloy will plate over the first component thus providing alternate layers of copper and nickel. The present invention comprises a process that allows one to electroform or electroplate a copper nickel alloy rather than laminated layers of copper and nickel.

BRIEF SUMMARY OF THE INVENTION Briefly, the invention comprises a process for electroforming or electroplating a nickel copper alloy by utilization of a nickel anode in an electroplating bath containing copper, nickel and boric acid.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows a schematic of a circuit used to electroform a copper nickel alloy;

FIG. 2 shows a graph of the voltage applied between the cathode and the anode as a function of time; and

FIG. 3 shows a second graph of the voltage applied between the cathode and the anode as a function of time.

DESCRIPTION OF THE PREFERRED PROCESS it has been discovered by utilization of a nickel anode with an electrolyte bath containing nickel, copper, a trace amount of wetting agent and sufficient boric acid to saturate the solution produces a suitable bath for electroforming alloys consisting of copper and nickel.

Utilizing the baths and the process of the present invention we have been able to electroplate nickel copper alloys having as much as 25% copper. Examples of the various electrolyte solutions will be given to illustrate the range and scope of the present invention, however, the shape of the applied voltage signal will now be described to illustrate the types of electrical signals suitable for use with the various electroplating baths.

Referring to FIG. 1, reference numeral 10 generally designates a schematic of an electrical circuit for applying the wave shape which we designate as a capacitor discharge bias plating technique. Reference numeral 11 designates an electroplating solution with reference numerals l2 and 13 denoting the anode and the cathode which are located in the electroplating solution of the present invention. Anode 12 connects to a power supply 14 through a resistor 16 and cathode 13 connects directly to power supply 14. Located across the outputs of power supply 14 is a capacitor 17 and a mercury relay switch 18 which is normally in the open position. Mercury relay switch 18 connects to a pulse generator 15 that supplies a signal to close mercury relay switch 18 at predetermined intervals.

In order to describe the shape of the electroplating signal obtained by using the circuit shown in FIG. 1, reference should also be made to FIG. 2. In order to begin electroplating, one places the electroplating solution in the electroplating tank 11. Next, one activates power supply 14. Typically, the voltage from power supply 14 may be on the order of 15 to 16 volts DC. At the same time, one sets pulse generator 15 to generate DC pulses at predetermined intervals. After activating power supply 14 and pulse generator 15, one begins electroplating. As the power is applied from power supply 14, it charges up capacitor 17. As a pulse signal from pulse generator 15 is fed into relay 18, it closes the relay contact which causes the capacitor to discharge across the anode 12 and cathode 13. The relay contact remains closed as long as the pulse signal is applied to relay 18, and once the pulse is removed, the contact in relay 18 opens removing all power between anode 12 and cathode l3.

FIG. 2 shows the shape of the applied signal utilizing this capacitor discharge technique. The voltage designated V indicates the maximum voltage or a portion of the voltage available at the capacitor as it begins to discharge. This voltage decays down to the voltage level V, where voltage signal remains until it is interrupted by opening the contact in relay switch 18. The cycle is then repeated. Typically, an entire cycle may have a duration of milliseconds, however, no limitation is intended thereto.

Referring to FIG. 3, the shape of another voltage signal as a function of time is shown. In essence, FIG. 3 shows DC voltage signal that is applied between anode 12 and cathode 13. The shape of the output signal is shown in FIG. 3 could be obtained by connecting a power supply 14 directly across anode 12 and cathode 13. Each of these waves forms offer certain advantages in electroforming a nickel copper alloy. With the wave shape shown in FIG. 2 we have been able to electroform nickel copper alloys that contain as much as 25% copper. In contrast with the wave shape shown in FIG. 1, we have been able to electroform a nickel copper alloy that contains about 8% to 10% copper but the electroforming rate been an order of magnitude faster than with the capacitor discharge bias signal. However, in both cases, the results were a nickelcopper alloy.

To better illustrate the various suitable electroplating solutions used, reference should be made to the following examples.

. Example No. 1

Amount Copper .38 grams] liter Nickel 90 grams/ liter Boric Acid Saturated solution pH of about I Wetting Agent Less than .l%

Example No. 2 Copper 2.26 grams/ liter Nickel 90 grams/ liter Boric Acid Saturated solution pH of about ll.5

Wetting Agent Less than .l% by volume Wetting Agent Less than 1% by volume The copper can be placed in solution by any suitable method, however, the preferred method is to use a copper sulfate solution or as a copper fluoborate solution. Similarly, the nickel can be placed in solution by any suitable method with the preferred method or a nickel fluoborate solution is used. The amount of copper specified in the examples is the actual amount of copper and not the amount of the sulfate or fluoborate solution.

In order to obtain the saturated solution of boric acid, the preferred method is to suspend a bag containing boric acid in-the solution and allow the boric acid to dissolve in the solution. By having sufficient boric acid in the bag the material dissolves in the solution until the solution is saturated.

In the above examples, the temperature of the bath was at about 40 C., however, wide variations of the C H C H SO Na. However, any number of wetting agents could be used as the function of the setting agent is to allow the electroplating bath to better wet the article and bring the fresh electroplating solution into contact with all regions on the plated article.

In the DC plating on the above examples, the current ranged from about to about 250 amps/square foot.

We claim:

l. A method of plating an alloy consisting of copper and nickel comprising the steps of:

a. providing an electroplating bath containing copper, nickel, and a boric acid solution;

b. providing a nickel anode and a cathode in said bath; and

c. applying between said nickel anode and said cathode a positive DC current of selected duration and magnitude, said current of selected duration and v magnitude having three periods, a first period of decreasing current, a second period of stabilized current and a third period of no current to thereby deposit a nickel copper alloy on said cathode.

2. The invention of claim 1 wherein the copper in said bath is at least .3 grams/liter.

3. The invention of claim 2 wherein the electroplating bath includes a wetting agent.

4. The invention of claim 1 wherein the current supplied between said anode and said cathode comprises a DC current.

5. The invention of claim 1 wherein the current supplied between said anode and said cathode comprises applying a low voltage signal of about 2 volts intermittent with a high voltage signal of about 15 volts.

6. The invention of claim 5 wherein the high voltage signal comprises a signal formed by a capacitor discharging.

7. The invention of claim 5 wherein the capacitive discharge voltage is followed by a low voltage DC signal followed by an off time.

8. The invention of claim 1 wherein the Ph of the solution is about 1.

9. The invention of claim 1 wherein the current density ranges from about 75 to about 250 amps/square foot. 

2. The invention of claim 1 wherein the copper in said bath is at least .3 grams/liter.
 3. The invention of claim 2 wherein the electroplating bath includes a wetting agent.
 4. The invention of claim 1 wherein the current supplied between said anode and said cathode comprises a DC current.
 5. The invention of claim 1 wherein the current supplied between said anode and said cathode comprises applying a low voltage signal of about 2 volts intermittent with a high voltage signal of about 15 volts.
 6. The invention of claim 5 wherein the high voltage signal comprises a signal formed by a capacitor discharging.
 7. The invention of claim 5 wherein the capacitive discharge voltage is followed by a low voltage DC signal followed by an off time.
 8. The invention of claim 1 wherein the Ph of the solution is about
 1. 9. The invention of claim 1 wherein the current density ranges from about 75 to about 250 amps/square foot. 